A new study shows that invasive blood clot removal is no more effective than standard treatment for severe ischemic stroke, even in patients with more functional brain tissue. (Image: Donald Erickson/iStockphoto.com

It seems logical that patients with more functional brain tissue after a severe ischemic stroke would reap greater benefits from removing the triggering clot than survivors with less viable tissue. But research presented today at the International Stroke Conference in Honolulu showed that clot removal was no more effective than standard antiplatelet therapy such as aspirin, even when researchers used brain scans to determine which patients with sufficient viable tissue might benefit from clot removal.

Invasive clot removal is considered a treatment option when patients don’t arrive at a hospital soon enough for the clot-busting drug tissue plasminogen activator (tPA) to work. Previous research shows that tPA is effective if given up to 4.5 hours after stroke symptoms begin.

In the new study, investigators enrolled 118 patients at 22 US medical centers within 5 to 6 hours of initial symptoms of stroke with blockages in large cerebral vessels. All patients underwent brain scans with magnetic resonance imaging (MRI) or computed tomography (CT) to assess blood flow and tissue viability.

Patients were randomly assigned either to the invasive procedure or to standard therapy and were treated within 8 hours of symptom onset. The researchers had hypothesized that patients with less than 70% of the brain dead because of blocked blood flow would have the best outcomes with clot removal.

Ninety days after treatment, about 21% of the patients had died, 4% had experienced cerebral hemorrhages serious enough to cause symptoms, and 58% had asymptomatic hemorrhages. However, brain scanning didn’t identify patients who would derive the most benefit from clot removal, and clot removal did not result in better functional outcomes than standard therapy in any of the patients.

“Our findings do not support the efficacy of using CT or MRI to select patients for acute stroke treatment or the efficacy of mechanical embolectomy with first-generation devices,” the researchers wrote in today’s New England Journal of Medicine, where the article is published. The first-generation clot-removal devices are at least 4 years old; newer ones have since come on the market.

In an accompanying editorial, Marc Chimowitz, MD, of the Medical University of South Carolina, said larger randomized trials testing the same hypothesis should be conducted with the newer clot-removal devices after data become available to show whether brain imaging accurately identifies viable brain tissue.